Syrian Rebels Seize U.N. Peacekeepers : The Two-WayThe U.N. Security Council demanded the immediate release of the 21 peacekeepers who were seized in the Golan Heights area between Syria and Israel. A Syrian rebel group called the Martyrs of Yarmouk claimed responsibility.

"The Secretary-General condemns the detention of 21 United Nations Disengagement Observer Force (UNDOF) peacekeepers by armed elements in the vicinity of Al Jamla in the area of limitation and calls for their immediate release.

"The Secretary-General reminds all actors in Syria that UNDOF is mandated to monitor the Disengagement of Forces Agreement between Israel and Syria. UNDOF's freedom of movement and safety and security must be respected by all parties."

The U.N. Security Council also demanded the "unconditional and immediate" release of the peacekeepers.

"A video uploaded on YouTube by a group that identified itself as the Martyrs of Yarmouk claimed responsibility and said the peacekeepers would be held until Syrian government forces withdrew from the area around Al Jamlah, the site of the weekend clashes. The video does not show any of the captives, but United Nations vehicles are visible.

"A speaker in the video warns in Arabic: 'If the withdrawal does not take place within 24 hours, we will deal with those guys like war prisoners. And praise to God.'

"The threat underscored the widening risk that the Syria conflict is destabilizing the Middle East, and raised new concerns about the agendas of some Syrian insurgent groups, just as Western nations, including the United States, were grappling over whether to arm them."

The capture of the peacekeepers comes a week after a member of the force was reported missing.

U.N. peacekeepers in the area monitor the 1974 disengagement accord between Syria and Israel after the 1973 Yom Kippur War between the two countries. The Security Council extended the mission's mandate in December 2012 for another six months, until June 30.

The development comes as Syrian rebels, over the past several days, have made significant gains in their campaign against the regime of President Bashar Assad.

U.S. Secretary of State John Kerry announced last week that the U.S. would provide $60 million in direct — non-lethal — aid to Syrian rebels.